1. Field of the Invention
This invention relates generally to fluid power systems which may include a fluid power device, in which it is desired to have a controlled rate of change of fluid flow, and to metering control valves for use in such systems.
2. Description of the Prior Art
Fluid power cylinders, i.e., hydraulic cylinders, are used as actuators in many applications. Double-acting cylinders which exert force upon both extension and retraction of the piston rod are commonly selectively actuated by a directional valve which applies fluid under pressure to one cylinder port for piston extension and to the other port for piston retraction. A pilot valve actuated by the directional valve is frequently included in the hydraulic system. Various devices have been incorporated in the cylinder for providing a cushioning action at the end of the piston stroke.
There are applications for hydraulic cylinders in which it is desirable to provide acceleration of the piston extension or retraction, other applications in which it is desirable to provide deceleration of the piston extension or retraction, and still other applications in which it is desirable to provide acceleration of the piston at the beginning of its stroke and deceleration at the end of its stroke.